This invention relates to a semiconductor pressure sensor and more particularly to a semiconductor pressure sensor useful in detecting pressure difference of two pressure sources.
One example of the conventional semiconductor pressure sensor is disclosed in Japanese Pat. Laid-Open No. 60-100026 for example, in which two sets of semiconductor pressure sensing units each including a diaphragm portion and four piezo-electric resistor elements connected in a bridge circuit are formed on a single common semiconductor substrate, and in which the fluid of which pressure is to be measured is applied to one of the pressure sensing units and two outputs from the respective bridge circuits are compared to make a subtraction, whereby any error due to residual distortions can be eliminated.
Another example of a semiconductor pressure sensor is disclosed in Japanese U. M. Laid-Open Pat. No. 61-87338. In this conventional pressure sensor, an opening is provided at the central portion cf a base and a pressure introducing conduit extends downwardly from the opening, and other openings for atmosphere are disposed remotely from the central opening. A pressure sensing diaphragm for detecting the pressure difference between the pressure introducing conduit and the atmospheric pressure is centrally disposed, and the opening for the atmospheric pressure is covered by the semiconductor chip which is covered by a cap.
In U.S. Pat. No. 4,895,026 to Tada, a disclosure is made as to a semiconductor pressure sensor comprising a first and a second identical pressure sensing diaphragm each having first and second pressure receiving surfaces and supported to align in a common plane in the same orientation. Two pressure sensing diaphragms have connected thereto similar bridge circuits made of piezoelectric elements for generating electrical signals indicative of the fluid pressure acting on the pressure sensing diaphragms. The semiconductor diaphragms are directly supported on an electrically insulating support frame held in a sensor housing. A first fluid passage connectable to a first pressure source is on communication with the first pressure receiving surface of the first diaphragm and the second pressure receiving surface of the second diaphragm, and a second fluid passage is in communication with a second pressure receiving surface of the first diaphragm and the first pressure receiving surface of the second diaphragm. The two electrical signals are supplied to a differential amplifier where two signals are subtracted and an output electrical signal proportional to the magnitude of the result of the subtracted between the first and the second electrical signals. During assembly, electrical terminals are molded in the housing, and the signal generating elements are mounted to one of the housing halves by the support plate, and then, the inner ends of the terminals and the signal generating elements are electrically connected by wires. These electrical components are covered by the second housing half.
Since the conventional semiconductor pressure sensors are constructed as above described, the support plate and the terminals are separate and discrete components, leading to the need for the separate manufacture and a poor productivity.